The US’s F-35 (JSF) is such a boondoggle and will end up being an absolute waste — so much so that no country will want to buy them or maintain them (despite what the military says or announces). That means the the more profitable the Russians are with their military jets the less their economy will suffer. The less the Russian suffer, the greater a power they become. Putin is an autocrat now; effectively a monarch. By building an unsalable fighter jet, the US has practically given Putin a license to build up its air military.